CAPTCHA has been widely deployed by commercial web sites as a security technology for purposes such as anti-spam. A common approach to evaluating the robustness of CAPTCHA is the use of machine learning techniques. Critical to this approach is the acquisition of an adequate set of labeled samples, on which the learning techniques are trained. However, such a sample labeling task is difficult fo...

Reflection is common when we see through a glass window, which not only visual disturbance but also influences the performance of computer vision algorithms. Removing reflection from single image, however, highly ill-posed since color at each pixel needs to be separated into two values belonging clear background and reflection, respectively. To solve this, existing methods use additional priors...

We explore the robustness and usability of movingimage object recognition (video) captchas, designing and implementing automated attacks based on computer vision techniques. Our approach is suitable for broad classes of moving-image captchas involving rigid objects. We first present an attack that defeats instances of such a captcha (NuCaptcha) representing the state-ofthe-art, involving dynami...

In this paper, we present a novel watermarking scheme to ensure the authenticity of digital images. Our authentication technique is able to detect malicious tampering of images even if they have been incidentally distorted by basic image processing operations. The image protection is achieved by the insertion of a secret author’s identification key in the image wavelet coefficients by their sel...